City Demonstrates How the World Turns

Italians reproduce the experiment that proved Earth turns on its axis, contending that a native son was the first one to drop the ball.

BOLOGNA, Italy — Cold rainwater was puddling on the red-marble floors of the San Petronio basilica late Saturday morning as several hundred people crowded at one end of the cavernous Gothic cathedral. They were on hand to watch a metal sphere, suspended by a 130-foot cord, crisscross a huge compass laid out like a carpet.

Under soaring pilasters and angelic frescoes, the ball swept back and forth, back and forth, rhythmically sweeping along the northwest-southeast axis. Propelled by an unseen magnetic force, the pendulum projected a red laser beam on the floor to show a steady clockwise shift measured in millimeters.

And so, the good people of Bologna re-created the experiment -- conducted 154 years ago by French physicist Jean-Bernard-Leon Foucault -- that proved Earth rotates on its axis.

"This is mystical," proclaimed Italian writer, philosopher and Bologna-area resident Umberto Eco, who helped lead the experiment with a team of scientists from the 917-year-old University of Bologna.

For The Record Los Angeles Times Thursday October 20, 2005 Home Edition Main News Part A Page 2 National Desk 1 inches; 65 words Type of Material: Correction Foucault pendulum -- An article in the Oct. 9 Section A about a Foucault pendulum in Bologna, Italy, where residents re-created the experiment that showed Earth turns on its axis, said that the pendulum ball swept back and forth "propelled by an unseen magnetic force." Although magnets keep the pendulum in motion, it is gravity and the Earth's rotation that cause the pendulum's shifting sweep.

Foucault has long received the credit for showing that our world goes round and round. In 1851, he invited members of the press to the Pantheon in Paris, wowing them with the movements of a giant pendulum that traced a shifting trajectory in the sand.

Eco named his second novel for the Frenchman's feat: "Foucault's Pendulum," a complex tale of intellectual gymnastics and Knights Templar intrigue.

But Bologna's city fathers contend it was one of their own who first performed the experiment, or at least attempted to. Six decades before Foucault, so the story goes, a monk named Giovanni Battista Guglielmini dropped weights from Bologna's 12th-century towers to show Earth's rotation. But the scientist flubbed his observation and calculation, and no one understood what he was talking about.

And so the honors went to Foucault.

Bologna, a mid-size city in northern Italy, had no trouble matching Foucault's theatrics in staging Saturday's stunt -- even the organizers didn't mind calling it that. Officials were hoping to encourage interest in the study of science in schools. And, if any promotion rubbed off on the city itself, well, that was icing on the cake.

With its sienna-colored palaces and miles of pretty porticoes, Bologna remains one of Italy's most attractive and relatively unspoiled cities, not yet overrun by tourists like Venice or Rome but with enough art and medieval architecture to make it worth visiting.

The Bolognesi, as the locals are known, who attended Saturday's ceremony were intrigued by the meeting of science, art and history inside the hazily lighted landmark church.

Giovanni Stoppa, 40, an engineer, brought his three children to see the metal-ball pendulum, and he carefully explained the scientific principle behind it to his eldest, Marta, 9.

Retired elementary school teacher Anna Galli, 75, carefully tracked the pendulum's slowly shifting path. "You can really see it," she said. "I studied all of this a very long time ago -- some of it I remember, some of it not. But for the young, to actually see the experiment, that's great."

A priest, speaking on behalf of the city's Roman Catholic Archbishop Carlo Caffarra, bestowed the church's blessing on the experiment, praising "man's creative genius" as seen through the ages -- Copernicus and Galileo and today's scientists. Of course, in the early 17th century, the church forced Galileo to recant his belief that Earth revolved around the sun, and denounced Foucault in his day as well. Times change.

Eco was, characteristically, philosophical. He said he was fascinated by Foucault's pendulum from the time he studied as a young man in Paris, and came to realize that there were hundreds of such pendulums in museums and academies the world over, all invoking a kind of reverence.